android emulator找不到avd_android avd can't find the emulator

    新的android SDK1.5提供了avd，可以更好的模拟真实环境。但是需要设置ANDROID_SDK_HOME环境变量，否则avd manger和android命令默认都会把新建的avd放到用户目录下，但emulator默认却不会到用户目录搜索。设置ANDROID_SDK_HOME后，大家都会到该目录下搜索。

不设的错误如下：

 Android Launch!
 adb is running normally.
Performing com.practice.hello.hello activity launch
Automatic Target Mode: Preferred AVD 'helloworld' is not available. Launching new emulator.
 Launching a new emulator with Virtual Device 'helloworld'

emulator: ERROR: unknown virtual device name

emulator: could not find virtual device named 'helloworld'